1. Field of the Invention
This invention relates to an elastic shaped article excelling in numerous physical properties including mechanical strength, thermal resistance, oil resistance, moldability and flexibility, which elastic shaped article is formed of a laminated material of at least two layers, i.e. one layer of soft polyvinyl chloride and one layer of other thermoplastic elastomer.
2. Description of the Prior Art
Heretofore, those ducts, hoses, tubes, sealing members and covering members which are used in transportation machines such as automobiles and motor bicycles, construction machines such as bulldozers, industrial machines such as robots, machine tools, hydraulic machines and pneumatic machines have been manufactured with vulcanized rubbers such as natural rubber and synthetic rubber. These raw materials pose problems due to exhaustibility of natural resources and involvement of a troublesome work of vulcanization. For the sake of the preservation of natural resources and the economization of energy, therefore, development of a new material capable of taking the place of vulcanized rubber has been longed for.
In various industrial fields, therefore, studies are being continued to explore the adoptability of such thermoplastic elastomers as soft polyvinyl chloride which obviate the necessity of vulcanization as the raw material for elastic shaped articles such as automotive boots which have hetetofore been preponderantly manufactured with vulcanized rubbers.
Generally, elastic shaped articles made of soft polyvinyl chloride exhibit high flexibility and enjoy relatively satisfactory elasticity and moldability. Unfortunately, they are inferior to the conventional elastic shaped articles made of vulcanized rubbers in terms of mechanical properties such as tensile strength and tear strength. They also suffer from a disadvantage that their flexibility is gradually impaired as their hardness is degraded with elapse of time. They have failed to find utility in applications which demand these properties. When these elastic shaped articles are used as boots in the steering units of automobiles, for example, they tend to sustain cracks under impacts frequently exerted by flying pebbles and the fitting parts serving to retain the boots in position tend to come out as the boots are gradually deprived of their flexibility. The elastic shaped articles of thermoplastic elastomers are further deficient in thermal resistance and in resistance to oils such as grease, gasoline and rubricants. They have, therefore, suffered from a disadvantage that they are not usable where they are liable to be heated to elevated temperatures or to be smeared with grease, gasoline and lubricants.
Despite the strong demand for the development of an ideal substitute for vulcanized rubbers as the raw material for elastic shaped articles such as boots, ducts, hoses, tubes and other members for use in various machines, there has not yet been perfected any elastic shaped article which excels in various properties such as flexibility, mechanical strength, thermal resistance and oil resistance and, moreover, enjoys high moldability.